[Accelo]

"What's everyone's thoughts on the 4L60 with Overdrive"

Just to be sure everyone is on the same page.
700R4 and 4L60's are the same transmission. 1982-1993.
I highly recommend the 1987-1993 version be used as the 4l60 went through a major upgrade in 1987.
The 4L60E and it's cousins (4L65E 4L70E) are the electronic versions and are not typically transplanted unless it's with a LSX motor.

The 4L60 makes an excellent transplant. I even ran on behind my 1971 C10 3/4T 396 BBC without issues. Of course I am not 16 anymore and I am assuming you wife drives like wife's do so no extrema duty change over is required unless maybe you are towing.

In Over-Drive the motor will act like it has 2.86 Gears if you were running a THM350 or any old style transmission with a 1:1 ratio in drive. To figure this out multiply the gear ratio by the over drive ratio, in this case it's .7 . (4.09*.7)
You also get a lower first gear which helps get the truck moving. Their are no downsides.

Removing the old manual transmission cross-member is likely the most difficult thing on this conversion. A flex plate, shortened driveline, dipstick tube, torque converter cover, and the automatic cross-member are required. Also the TV cable and the bracket for the intake manifold. Be sure to get the correct bolts for the torque converter as they will be metric. Installing the wiring for the lock-up converter is optional. Expect another 3% increase in highway mileage if you set this up. It is covered in other threads.

I set mine up shift indicator so drive was OD and park and neutral lined up. I just relocated the factory 350thm bracket by moving on leg of the frame adapter. The shift linkage lined up fin after that. The indicator just didn't indicate "manual first gear" which was fine. My BBC went from 10mph to 13mph on my 3/4T with the same gears. That's a 30% improvement. You may get the same 30% but start from a better number than the 10mph I was getting.
You will love it.
Cheers.